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废气排放的电脑控制1970年美国国会通过一项限制汽车废气排放量的法令。在此以前人们还没意识到,这些废气对环境污染的严重性究竟有多大。七十年代早期的废气控制系统,不过是利用大容量空气泵所构成的一套封闭型废气再循环系统。它能使一些未燃尽的废气再度氧化,然而其效率比今天的电子设备加复杂的催化系统,当然要逊色多了。废气中有害成份主要有四种:碳氢化合物(HC),一氧化碳(CO),氮氧化合物(NOx)和铅(Pb)化物。由于铅化物的排放与机械问题无关,这里就不谈了。众所周知,提高燃烧温度有利于减少CO和HC的含量,但遗憾的是也会随之而提高NOx的含量。要同时解决这对矛盾是很困难的。然而,仅仅在几年前才发现,NOx只有在某一个高峰温度才会开始产生,在低于此温度时仍然可以通过延长燃烧时间,来氧化掉多余的HC和CO。
Computer Control of Exhaust Emissions In 1970, the United States Congress passed a law to limit emissions from vehicles. Prior to this people have not realized that the extent of the seriousness of these emissions on the environment pollution. The exhaust control system in the early 1970s was a closed-loop exhaust gas recirculation system using a large-capacity air pump. It can reoxidize some of the unburned waste gas, but its efficiency is certainly less than today’s electronic devices plus sophisticated catalytic systems. There are mainly four types of harmful components in exhaust gas: hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx) and lead (Pb) compounds. Since the emissions of lead compounds have nothing to do with mechanical problems, we will not talk about them here. It is well-known that raising the combustion temperature helps to reduce the contents of CO and HC, but regrettably increases the NOx content. It is very difficult to solve this contradiction at the same time. However, it was only a few years ago that NOx was only started to occur at a certain peak temperature, and below this temperature it was possible to oxidize excess HC and CO by lengthening the burn-in time.